The present invention relates to an ultrasound diagnostic apparatus, an ultrasound image generation apparatus, and an ultrasound image generation method. More particularly, the invention relates to an ultrasound diagnostic apparatus, an ultrasound image generation apparatus, and an ultrasound image generation method used when displaying a puncture tool on a screen together with body tissues, specifically when displaying the tip end of a puncture tool such as a puncture needle in an ultrasound image in an accurate and appropriate manner when performing paracentesis.
In medical fields, an ultrasound image generation apparatus for generating ultrasound images and an ultrasound diagnostic apparatus using the generated ultrasound images have been put into practical use and are used widely for diagnosis and examination. In general, this kind of ultrasound image generation apparatus and ultrasound diagnostic apparatus (hereinafter referred collectively to as an ultrasound diagnostic apparatus) includes an ultrasound probe including an array of vibrators therein and a diagnostic apparatus main body connected to the ultrasound probe. In the ultrasound diagnostic apparatus, the ultrasound probe transmits ultrasound waves toward a subject to be examined, that is to say, a patient to thereby irradiate the patient with the ultrasound waves. Then, the ultrasound probe receives echoes (reflection sound) of the ultrasound waves reflected from the patient, namely signals (hereinafter referred to as echo signals) originating from ultrasound echoes from the subject. The received echo signals are electrically processed by the diagnostic apparatus main body whereby ultrasound tomographic images of the patient, called ultrasound images are generated and displayed on a monitor or the like.
Moreover, the ultrasound diagnostic apparatus is also used when a physician performs a paracentesis which involves inserting a puncture tool, for example, a puncture needle, in a desired site to collect a tissue sample for the purpose of diagnosing cell tissues.
In the paracentesis, it is important to enable the puncture needle to be observed on a monitor, namely as an image and to allow the puncture needle to reach a target object. To allow the puncture needle to certainly reach a target object or a target site, the physician inserts the puncture needle along a predetermined insertion path (a path along which the puncture needle is inserted within the body of a patient) while observing ultrasound images. Moreover, when establishing a definitive cancer diagnosis such as cell tissue diagnosis based on biopsy or the like, it is also important to capture and store an image in which the puncture needle is inserted into a target object as an evidence image.
When performing such paracentesis, it is necessary to allow the puncture needle to reach a treatment target such as a target site or a target object and to perform drainage of excess fluid from the treatment target or perform injection (PEIT) of a substance to the treatment target. Thus, it is important to observe the puncture needle, particularly, the tip end thereof, on a monitor (ultrasound image) in a reliable, accurate, and appropriate manner.
To solve this problem, according to an ultrasound imaging technique disclosed in Patent Document 1 (JP 4030644 B), in order to detect the accurate tip position of a puncture needle inserted into a subject to be examined, the puncture needle is inserted while being mechanically vibrated by a vibration imparting mechanism attached to the base end thereof, whereby a Doppler image of the puncture needle is obtained based on a Doppler signal and displayed so as to be superimposed on a B-mode image to thereby obtain the image of the puncture needle.
According to an ultrasound diagnostic apparatus disclosed in Patent Document 2 (JP 2001-269339 A), B-mode ultrasound tomographic image frame data obtained by an ultrasound probe are stored in a memory, a difference between the previous frame data and the presently obtained frame data is calculated to obtain a spatial variation as digital data, and the digital data is added to the presently obtained frame data, whereby a desired puncture needle image is displayed in a B-mode ultrasound image. As a result, the technique of Patent Document 2 can display a clear puncture needle image based on only the B-mode ultrasound tomographic image frame data without using the vibration imparting mechanism and Doppler-mode processing which were necessary in the ultrasound imaging technique disclosed in Patent Document 1.
According to an ultrasound-guided puncture system disclosed in Patent Document 3 (JP 2000-107178 A), signals received by an ultrasound probe, transmitted from a subject to be examined into which a puncture needle is inserted are processed to generate B-mode image signals, and a B-mode ultrasound tomographic image is displayed on a display device based on the B-mode image signals. Moreover, a portion which has a higher luminance than the ultrasound image being displayed and in which the luminance varies abruptly is extracted and colored, and the colored extracted portion is displayed so as to be superimposed on an updated ultrasound tomographic image. As a result, the technique of Patent Document 3 can provide an inexpensive ultrasound-guided puncture system capable of performing treatment and examination in a reliable and satisfactory manner without missing the tip position of a puncture needle inserted once into a patient.
Moreover, Patent Document 4 (JP 2006-346477 A) discloses an ultrasound diagnostic apparatus as an apparatus for displaying a puncture guide line serving as a guide for inserting a puncture needle, in which an advancing angle of the puncture needle is calculated from a linear ultrasound echo signal of a predetermined length or longer, and a puncture guide line corresponding to the advancing angle is displayed so as to be superimposed on a B-mode image which is an ultrasound image generated from echo signals.
Furthermore, Patent Document 5 (JP 8-299344 A) discloses an ultrasound diagnostic apparatus in which the amount of shift between an insertion path along which a puncture needle is inserted and a predetermined puncture guide line is detected, and the guide line is moved from a reference trajectory corresponding to a reference position of the puncture needle so as to match the ultrasound image of the puncture needle with the guide line to thereby display a corrected puncture guide line.
In paracentesis, since the burden on a patient and the degree of invasiveness decrease as the puncture needle becomes narrower, a puncture needle which is as narrow as possible is used depending on a risk or the like. However, as the puncture needle becomes narrower, the ability to draw it on an ultrasound image also decreases, and the puncture needle is displayed in a disconnected manner.
To solve this problem, Patent Document 6 (JP 2006-320378 A) discloses an ultrasound diagnostic apparatus in which a plurality of images are acquired by irradiating ultrasound waves in a direction where strong echo signals are obtained, and the images are combined and displayed so as to suppress a puncture needle from being displayed in a disconnected manner. Moreover, Patent Document 7 (JP 2007-222264 A) discloses an ultrasound diagnostic apparatus which displays a clear image of a tissue structure while suppressing speckles by adaptively changing image processing conditions in accordance with a local property of the tissue.